Gas Exchange In Bony Fish

Question 1

What features to gills have that makes them effective for gas exchange
(SA)

Answer 1

Lots of Gill filaments covered in lamellae

Lamellae are thin + blood capillaries near surface gives short diffusion distance

Question 2

What features do gills have that makes them effective for gas exchange
(Blood flow)

Answer 2

Is counter current to water flow maintaining concentration gradient gradient along the entire length of the exchange system.

Continuous flow of blood through a rich network of capillaries, continual refreshing of oxygenated blood, keeping concentration gradient.

Question 3

What features to gills have that makes them effective for gas exchange
(Water)

Answer 3

Continuous flow of water, continual refreshing of oxygenated water, maintain concentration gradient

Question 4

Gill filaments

Answer 4

Occur in large stacks
Flow of water keeps them apart
Exposing a larger SA for gaseous exchange

Question 5

Efferent blood vessel

Answer 5

Carries blood leaving the gills in the opposite direction to the incoming water maintaining a steep concentration gradient

Question 6

Afferent blood vessel

Answer 6

Brings blood into the system

Carries blood towards Gill filaments/ lamellae

Question 7

Why can bony fish not rely on diffusion alone

Answer 7

Big fish such as trout and cod are relatively big and active so have a high oxygen demand.
They also have small SA:V therefore diffusion would not be enough to satisfy oxygen needs

Question 8

Gill lamellae

Answer 8

Found on the Gill filaments
Rich blood supply
Large SA:V
Main site of gaseous exchange

Question 9

Mechanism of ventilation

Answer 9

Fish opens its mouth, which lowers the floor of the buccal cavity

• volume of the buccal cavity increases, decreasing the pressure, water is then sucked in
• when mouth closes the floor of the buccal cavity is raised, volume inside the cavity decreases, pressure increases and water is forced out across the gill filaments
• each gill is covered by a bony flap called the operculum, the increase in pressure forces the operculum on each side of the head to open, allowing water to leave the gills

Question 10

Counter current flow

Answer 10

Blood and water flow in opposite directions
So oxygen concentration gradient between water and blood is maintained along the gill
O2 continues to diffuse down the concentration gradient so a much higher level of overall oxygen saturation is achieved